[turbofan] Reduce (x & K) & K to x & K.

src/compiler/machine-operator-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/machine-operator-reducer.h"
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/codegen.h"
 #include "src/compiler/generic-node-inl.h"
@@ skipping 91 matching lines @@
     case IrOpcode::kProjection:
       return ReduceProjection(OpParameter<size_t>(node), node->InputAt(0));
     case IrOpcode::kWord32And: {
       Int32BinopMatcher m(node);
       if (m.right().Is(0)) return Replace(m.right().node());  // x & 0  => 0
       if (m.right().Is(-1)) return Replace(m.left().node());  // x & -1 => x
       if (m.IsFoldable()) {                                   // K & K  => K
         return ReplaceInt32(m.left().Value() & m.right().Value());
       }
       if (m.LeftEqualsRight()) return Replace(m.left().node());  // x & x => x
+      if (m.left().IsWord32And() && m.right().HasValue()) {
+        Int32BinopMatcher mleft(m.left().node());
+        if (mleft.right().HasValue()) {  // (x & K) & K => x & K
+          node->ReplaceInput(0, mleft.left().node());
+          node->ReplaceInput(
+              1, Int32Constant(m.right().Value() & mleft.right().Value()));
+          return Changed(node);
+        }
+      }
       break;
     }
     case IrOpcode::kWord32Or: {
       Int32BinopMatcher m(node);
       if (m.right().Is(0)) return Replace(m.left().node());    // x | 0  => x
       if (m.right().Is(-1)) return Replace(m.right().node());  // x | -1 => -1
       if (m.IsFoldable()) {                                    // K | K  => K
         return ReplaceInt32(m.left().Value() | m.right().Value());
       }
       if (m.LeftEqualsRight()) return Replace(m.left().node());  // x | x => x
@@ skipping 584 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8